Arsène Wenger initially prowled his technical area wearing the sort of lightweight suit ideal for gentle spring afternoons in southern Europe. By tea-time the severe windchill whipping off the River Wear had long ensured that most sensible spectators were properly gloved, scarved and over-coated but, seemingly immune to the plunging mercury, Arsenal's manager began the evening defiantly under-dressed.

Well before half-time Wenger, realising his misjudgment, finally zipped himself into the swaddling folds of the warmest of managerial duvet coats. By then, though, his team had been caught cold and were destined to suffer their second calamity in a torrid four days which began with a chastening 4-0 Champions league thrashing in Milan.

While Alex Song seemed rather taken aback at being repeatedly knocked off the ball and out of his stride by O'Neill's excellent holding midfielder, Lee Cattermole, Mikel Arteta looked shocked to find himself second guessed at virtually every turn. Although Arteta enjoyed plenty of possession, Cattermole and company ensured the Spaniard was not permitted the room required to show off his creative passing, thereby leaving Robin van Persie and the returning Gervinho deeply frustrated.

"We are hard to beat and I thought we wanted it more than Arsenal," said Cattermole, who must harbour outside hopes of gatecrashing England's Euro 2012 squad. "We tackled well, we passed well and were the better side. Arsenal had a lot of the ball but never really hurt us. We'd set ourselves up right and were very organised."

The goalkeeper Simon Mignolet, well protected throughout by outstanding central defensive performances from John O'Shea and Michael Turner, made only one really significant save, performing acrobatic wonders to tip away Gervinho's first-half shot. Wenger was adamant that his side – in which the ultimately injured Aaron Ramsey again proved worryingly peripheral – should have had a penalty when Van Persie collapsed under O'Shea's challenge but Howard Webb adjudged the defender to have got a toe to the ball first.

Shortly afterwards Sunderland scored. The accident-prone Johan Djourou's typically unnecessary foul on Craig Gardner resulted in a free-kick swung in by Sebastian Larsson, once of Arsenal. Semi-cleared by Thomas Vermaelen, it fell to the unmarked Kieran Richardson's left foot, the ball taking a slight deflection off Sébastien Squillaci – on for the hamstrung Francis Coquelin – en route to the bottom corner.

Wenger's cause is hampered by a raft of defensive battle wounds sufficiently serious to fill an episode or three of Casualty. Stripped of the injured Per Mertesacker and Laurent Koscielny, and with Vermaelen forced to switch to his less favoured left-back role, that visiting backline appeared fazed every time ç, Sunderland's impressive lone striker, or James McClean, O'Neill's dynamic left-winger, ran at them.

"Sess and McClean have been great for us," said Cattermole. "They both have pace and they can beat a man, so they're great at taking the pressure off the rest of the team. When the opposition have a lot of possession and you're working really hard, it's great to be able to give them the ball. You know they can beat a man, take it 30 yards up the pitch and give you a breather."

Wenger must have hoped Alex Oxlade-Chamberlain would provide a similar outlet for his side but O'Neill's five-man midfield stifled the young winger. Confirmation that it was not Oxlade-Chamberlain's night arrived when, frantically back-tracking, he turned the ball into his own net after Larsson's shot rebounded off a post at the end of a move which began with Arteta slipping over and featured the fast-breaking Sessègnon accelerating smoothly away from all-comers.

O'Neill's unique amalgam of inspirational motivation and cleverly effective choreography had claimed another scalp. "Whoever we're up against, we go into every game believing we can win," said Cattermole. "Everyone in our dressing room will be thinking we've a real chance of winning the FA Cup."

From the warmth of an ITV pundit's vantage point Roy Keane claimed that he had known Arsenal were doomed from the first minute. The reason? "Five or six of their players were wearing gloves," he said. "No professional footballer worth his salt should enter the field of play in gloves."

If Wenger, who justifiably emphasised his team's considerable fatigue at the end of an eight-day period featuring three away trips, was entitled to roll his eyes at that assessment, Keane's subsequent comment may just have hit a raw nerve. "Arsenal's players should have been worried about playing for their manager, not about getting cold hands," said Manchester United's former captain.

Only time will tell whether a defiant Wenger protested too much when he repeatedly praised Arsenal's spirit but Cattermole's reiteration that "we wanted it more" was not entirely reassuring.